[RFC][PATCH] add driver matching priorities

[Adam Belay <abelay@novell.com>]

Hi,

This patch adds initial support for driver matching priorities to the
driver model.  It is needed for my work on converting the pci bridge
driver to use "struct device_driver".  It may also be helpful for driver
with more complex (or long id lists as I've seen in many cases) matching
criteria. 

"match" has been added to "struct device_driver".  There are now two
steps in the matching process.  The first step is a bus specific filter
that determines possible driver candidates.  The second step is a driver
specific match function that verifies if the driver will work with the
hardware, and returns a priority code (how well it is able to handle the
device).  The bus layer could override the driver's match function if
necessary (similar to how it passes *probe through it's layer and then
on to the actual driver).

The current priorities are as follows:

enum {
	MATCH_PRIORITY_FAILURE = 0,
	MATCH_PRIORITY_GENERIC,
	MATCH_PRIORITY_NORMAL,
	MATCH_PRIORITY_VENDOR,
};

let me know if any of this would need to be changed.  For example, the
"struct bus_type" match function could return a priority code.

Of course this patch is not going to be effective alone.  We also need
to change the init order.  If a driver is registered early but isn't the
best available, it will be bound to the device prematurely.  This would
be a problem for carbus (yenta) bridges.

I think we may have to load all in kernel drivers first, and then begin
matching them to hardware.  Do you agree?  If so, I'd be happy to make a
patch for that too.

Thanks,
Adam


--- a/drivers/base/bus.c	2005-01-20 17:37:46.000000000 -0500
+++ b/drivers/base/bus.c	2005-01-28 16:59:00.000000000 -0500
@@ -286,6 +286,9 @@
 	if (drv->bus->match && !drv->bus->match(dev, drv))
 		return -ENODEV;
 
+	if (drv->match && !drv->match(dev))
+		return -ENODEV;
+
 	dev->driver = drv;
 	if (drv->probe) {
 		int error = drv->probe(dev);
@@ -299,6 +302,42 @@
 	return 0;
 }
 
+/**
+ *	driver_probe_device_priority - attempt to bind device & driver with a
+ *				       given match level priority 
+ *	@drv:		driver.
+ *	@dev:		device.
+ *	@priority	the match level priority
+ */
+
+static int driver_probe_device_priority(struct device_driver * drv,
+					struct device * dev, int priority)
+{
+	int matchp;
+
+	if (drv->bus->match && !drv->bus->match(dev, drv))
+		return -ENODEV;
+
+	if (drv->match) {
+		matchp = drv->match(dev);
+	} else
+		matchp = MATCH_PRIORITY_NORMAL;
+
+	if (matchp != priority)
+		return -ENODEV;
+
+	dev->driver = drv;
+	if (drv->probe) {
+		int error = drv->probe(dev);
+		if (error) {
+			dev->driver = NULL;
+			return error;
+		}
+	}
+
+	device_bind_driver(dev);
+	return 0;
+}
 
 /**
  *	device_attach - try to attach device to a driver.
@@ -312,17 +351,20 @@
 {
  	struct bus_type * bus = dev->bus;
 	struct list_head * entry;
-	int error;
+	int error, matchp = MATCH_PRIORITY_VENDOR;
 
 	if (dev->driver) {
 		device_bind_driver(dev);
 		return 1;
 	}
 
-	if (bus->match) {
+	if (!bus->match)
+		return 0;
+		
+	while (matchp > 0) {
 		list_for_each(entry, &bus->drivers.list) {
 			struct device_driver * drv = to_drv(entry);
-			error = driver_probe_device(drv, dev);
+			error = driver_probe_device_priority(drv, dev, matchp);
 			if (!error)
 				/* success, driver matched */
 				return 1;
@@ -332,6 +374,7 @@
 				    "%s: probe of %s failed with error %d\n",
 				    drv->name, dev->bus_id, error);
 		}
+		matchp--;
 	}
 
 	return 0;
--- a/include/linux/device.h	2005-01-20 17:37:26.000000000 -0500
+++ b/include/linux/device.h	2005-01-28 16:40:22.000000000 -0500
@@ -41,6 +41,13 @@
 	RESUME_ENABLE,
 };
 
+enum {
+	MATCH_PRIORITY_FAILURE = 0,
+	MATCH_PRIORITY_GENERIC,
+	MATCH_PRIORITY_NORMAL,
+	MATCH_PRIORITY_VENDOR,
+};
+
 struct device;
 struct device_driver;
 struct class;
@@ -108,6 +115,7 @@
 
 	struct module 		* owner;
 
+	int	(*match)	(struct device * dev);
 	int	(*probe)	(struct device * dev);
 	int 	(*remove)	(struct device * dev);
 	void	(*shutdown)	(struct device * dev);